Heat exchanger

ABSTRACT

A heat exchanger, in particular for fluid cooling devices, having a package of plane-parallel plates ( 1 ), with flow regions ( 3, 5 ) for a hot medium and for a cooling medium being formed in alternation between pairs of plates ( 1 ) lying on top of one another, said regions each being laterally bordered by profile strips ( 7, 11 ) which keep the plates ( 1 ) at a distance and which form solder surfaces ( 25 ) which adjoin the plates ( 1 ), the profile strips ( 7, 11 ) on the flow regions ( 3, 5 ) of one medium and the other medium extending along edges of the plates ( 1 ) abutting one another at an angle and at least the profile strips ( 11 ) of the flow regions ( 5 ) of the cooling medium having a base body ( 13 ), two legs ( 17 ) extending from the base body along the solder surfaces ( 25 ), and between the legs a recess ( 15 ) which is open toward the adjacent flow region ( 5 ), is characterized in that the recess ( 15 ) at least in the region adjacent to its inner end segment ( 23 ) is bordered by planar wall parts ( 29 ).

The invention relates to a heat exchanger, in particular for fluid cooling devices, having a package of plane-parallel plates, with flow regions for a hot medium and for a cooling medium being formed in alternation between pairs of plates lying on top of one another, said regions each being laterally bordered by profile strips which keep the plates at a distance and which form solder surfaces which adjoin the plates, the profile ships on the flow regions of one medium and the other medium extending along edges of the plates abutting one another at an angle and at least the profile strips of the flow regions of the cooling medium having a base body, two legs extending from the base body along the solder surfaces, and between the legs a recess which is open toward the adjacent flow region.

Heat exchangers of this type, also referred to as finned radiators, are prior art, compare DE 20 208 748 U1. Such heat exchangers are often used, with air as the cooling medium, for cooling of hydraulic fluids for the working hydraulics of mechanical systems, such as construction machinery or the like, for hydrostatic drives, or as oil coolers for highly loaded gear trains, specifically for wind power plants. In the operation of such systems, the heat exchangers are exposed not only to mechanical loads, but, due to the high operating temperatures of fluids to be cooled, in particular also to thermal loads. This is especially the case when temperature jumps arise due to intermittent operating modes; as a result of material strain, this leads to serious stresses in the package of components which are joined into a rigid block by soldering. The consequences are stress cracks, especially in the area of the solder seams, with the risk of failure of the heat exchanger and thus endangerment of the pertinent system.

With respect to these problems the object of the invention is to provide a heat exchanger which is characterized by improved resistivity to operating loads so that reliable long-term operation is enabled.

This object is achieved according to the invention by a heat exchanger having the features of claim 1 in its entirety.

According to the characterizing part of claim 1, one essential particularity of the invention consists in that the shape of the cross section bordering the solder surfaces is optimized in terms of avoiding undue stresses by special shaping of the recess at least of the profile strips which border the cooling medium. In that, starting from the inner end section, the recess has planar wall parts, an at least more or less linear change of the bending strength over the length of the profile legs can be achieved so that optimum bending behavior of the legs can be attained by the choice of the length and/or tilt of these planar wall parts relative to the plane of the solder surface.

Especially advantageously, the arrangement here can be such that the recess, starting from its inner end section, has diverging first planar wall parts which extend to constrictions of the cross section of the legs, converging second planar wall parts which adjoin the constrictions, and third planar wall parts which adjoin said second planar wall parts and which extend parallel to the solder surfaces into the vicinity of the opening of the recess. In this way, on the profile legs, areas of lower bending strength are formed which are connected on both sides to leg segments in which the bending resistance increases essentially linearly. The constrictions define not only a bending line of the flector type, but also represent the site of the steepest temperature gradient. Since the latter takes effect at the site of the smallest material cross section, correspondingly small material strains and stresses arise.

In especially advantageous exemplary embodiments, the recess is shaped such that fourth planar wall parts which run slightly diverging to one another as far as the opening of the recess adjoin the third planar wall parts.

Preferably, the first planar wall parts can form planes which are perpendicular to one another, and the second planar wall parts can include an obtuse angle with the first planar wall parts, which angle is preferably slightly larger than a right angle. Thus the cross-sectional shape of the recess in the region bordering the inner end corresponds more or less to a square which is open toward the opening.

Advantageously, the arrangement can be made such that the first planar wall parts are connected to one another and to the second planar wall parts by way of arched wall sections with the same radius of curvature. The second planar wall parts are connected to the third planar wall parts and the latter are connected to the fourth planar wall parts, preferably, also by way of arched wall sections with the same second radius of curvature which is twice the first radius of curvature.

With respect to the dimensioning of the constrictions relative to the cross-sectional thickness of the legs which follow in the direction to the opening, the arrangement is preferably made such that the thickness of the cross section of the legs in the region of the third planar wall parts is roughly twice the thickness of the cross section at the constrictions.

The invention is detailed below using the drawings:

FIG. 1 shows as an exploded perspective oblique view only one corner region of one part of the plate package of one exemplary embodiment of the heat exchanger according to the invention and

FIG. 2 shows an enlarged side view of only one profile strip for forming a spacer between the plates of the package.

FIG. 1 illustrates one exemplary embodiment in the form of a heat exchanger manufactured in the conventional plate design with a stack of flat plates 1, preferably of an aluminum alloy, which run in parallel planes and form separating plates for the flow regions located between them, between each succeeding pairs of plates one flow region 3 for the medium to be cooled, for example, hydraulic oil, and one flow region 5 for a cooling medium, for example, cooling air, being formed in alternation. As is apparent from FIG. 1, the flow regions 3 and 5 extend at a right angle to one another. The flow region 3, which is at the top in the drawings, for the hot medium is closed on two opposite sides by cover strips 7 of conventional design and between which the respective inflow and outflow region is located, between the cover strips 7 conventional turbulators 9 being provided in the form of fins.

The flow region 5 of the cooling medium is likewise bordered laterally by cover strips which form the spacers between the respective pair of plates and which are made as profile strips 11 with a special configuration according to the invention. This design according to the invention is detailed using FIG. 2.

As is apparent, the profile strips 11, which are likewise preferably extruded from an aluminum alloy, have a square or block-shaped base body 13 which faces the edge region of the plates 1, a recess 15 in the form of a continuous longitudinal groove, and legs 17 which border the recess 15 on both sides. As FIG. 1 shows, the recess 15 is open toward the flow region 5 in which cooling fins 19 are located which, analogous to the turbulators 9 in the flow region 3, enlarge the effective heat transfer surface. The inner end section 23 (FIG. 2) of the recess 15 is located at a distance from the closed end 21 of the profile strip 11, which is somewhat greater than the distance between the end section 23 and opening of the recess 15. The flat upper and lower end surfaces of the profile strip 11, that is to say, from the base body 13 to the end region of the legs 17, form the solder surfaces 25 for connecting the plate package. There are lip-like projections 27 on the open end of the recess 15. As FIG. 1 shows, the lips 27 support the fins 5 in front of the end of the solder surfaces 25, so that the danger that fin ends will penetrate into the gap between the plate 1 and solder surface 25 is avoided in stack formation.

The recess 15, starting from its inner end segment 23, is bordered by planar wall parts 29 which, diverging and including a right angle to one another, extend into the vicinity of the pertinent solder surface 25 and there form a profile constriction 31 of the profile cross section of the legs 17. The constriction 31 is adjoined by second planar wall parts 33 which run converging to one another and include an obtuse angle which is slightly larger than a right angle with the first planar wall parts 29. The length of these second planar wall parts 33 is somewhat less than the length of the first planar wall parts 29, and these second planar wall parts 33 are followed by third planar wall parts 35 which define planes which are parallel to the solder surfaces 25, and which latter parts extend into the vicinity of the opening of the recess 15. These third planar wall parts are in turn followed by fourth planar wall parts 37 which extend slightly diverging to one another as far as the opening of the recess 15. The connection of the first planar wall parts 29 to one another and to the second planar wall parts 33 takes place by way of arched wall sections 39 with the same radius of curvature. The connection of the second planar wall parts 33 to the third planar wall parts 35 and the latter to the fourth planar wall parts 37 likewise takes place by way of arched wall sections 41 in which the radius of curvature is twice the radius of curvature at the wall sections 39.

The cross-sectional shape of the recess 15 provided according to the invention results in an effective reduction of operating stress peaks and the risk of crack formation at the solder sites. When the coolant is flowing through the recess 15, the constrictions 31 on the leg profile form the site of the steepest temperature gradient. At the same time, this is also the location of the smallest material cross section so that thermal deformations are limited to correspondingly limited material portions. Since the profile thickness of the legs 17, starting from the constrictions 31, toward the opening, increases to a profile thickness which corresponds roughly to twice the value at the constrictions 31, an optimum stress distribution over the region of the solder surfaces 25 is achieved.

The heat exchanger means according to the invention need not be limited to the field of fluid cooling, but can also be used in general for cooling of gaseous media and here can include in particular charge-air coolers (diesel engines) as well as aftercoolers and intercoolers (compressors). The temperature differences (cooling air to the medium) in these applications are comparatively much higher than described in the foregoing. 

1. A heat exchanger, in particular for fluid cooling devices, having a package of plane-parallel plates (1), with flow regions (3,5) for a hot medium and for a cooling medium being formed in alternation between pairs of plates (1) lying on top of one another, said regions each being laterally bordered by profile strips (7, 11) which keep the plates (1) at a distance and which form solder surfaces (25) which adjoin the plates (1), the profile strips (7, 11) on the flow regions (3, 5) of one medium and the other medium extending along edges of the plates (1) abutting one another at an angle and at least the profile strips (11) of the flow regions (5) of the cooling medium having a base body (13), two legs (17) extending from the base body along the solder surfaces (25), and between the legs a recess (15) which is open toward the adjacent flow region (5), characterized in that the recess (15) at least in the region adjacent to its inner end segment (23) is bordered by planar wall parts (29).
 2. The heat exchanger according to claim 1, characterized in that the recess (15), starting from its inner end section (23), has diverging first planar wall parts (29) which extend to constrictions (31) of the cross section of the legs (17), converging second planar wall parts (33) which adjoin the constrictions (31), and third planar wall parts (35) which adjoin said second planar wall parts and which extend parallel to the solder surfaces (25) into the vicinity of the opening of the recess (15).
 3. The heat exchanger according to claim 1, characterized in that fourth planar wall parts (37) which run slightly diverging to one another as far as the opening of the recess (15) adjoin the third planar wall parts (35).
 4. The heat exchanger according to claim 1, characterized in that the first planar wall parts (29) form planes which are perpendicular to one another.
 5. The heat exchanger according to claim 1, characterized in that the second planar wall parts (33) include an obtuse angle with the first planar wall parts (29).
 6. The heat exchanger according to claim 1, characterized in that the first planar wall parts (29) are connected to one another and to the second planar wall parts (33) each by way of arched wall sections (39) with the same first radius of curvature.
 7. The heat exchanger according to claim 1, characterized in that the second planar wall parts (33) are connected to the third planar wall parts (35) and the latter are connected to the fourth planar wall parts (37) by way of arched wall sections (41) with the same second radius of curvature which is twice the first radius of curvature.
 8. The heat exchanger according to claim 1, characterized in that the thickness of the cross section of the legs (17) in the region of the third planar wall parts (35) is roughly twice the thickness at the constrictions (31). 